convert public key from newline delimited string to a real array

Added a compatibility layer that will convert newline delimited keys to array
when the user is fetched from the database.
This code will be removed in future versions please update your public keys,
you only need to resave the users using the REST API.

api/internal_test.go

@@ -42,12 +42,12 @@ func TestCheckUser(t *testing.T) {
 		t.Errorf("actual password must be nil")
 	}
 	actual.Password = ""
-	actual.PublicKey = "pub key"
+	actual.PublicKey = []string{"pub key"}
 	err = checkUser(expected, actual)
 	if err == nil {
 		t.Errorf("actual public key must be nil")
 	}
-	actual.PublicKey = ""
+	actual.PublicKey = []string{}
 	err = checkUser(expected, actual)
 	if err == nil {
 		t.Errorf("actual ID must be > 0")